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<FONT color="green">001</FONT>    /*<a name="line.1"></a>
<FONT color="green">002</FONT>     * Licensed to the Apache Software Foundation (ASF) under one or more<a name="line.2"></a>
<FONT color="green">003</FONT>     * contributor license agreements.  See the NOTICE file distributed with<a name="line.3"></a>
<FONT color="green">004</FONT>     * this work for additional information regarding copyright ownership.<a name="line.4"></a>
<FONT color="green">005</FONT>     * The ASF licenses this file to You under the Apache License, Version 2.0<a name="line.5"></a>
<FONT color="green">006</FONT>     * (the "License"); you may not use this file except in compliance with<a name="line.6"></a>
<FONT color="green">007</FONT>     * the License.  You may obtain a copy of the License at<a name="line.7"></a>
<FONT color="green">008</FONT>     *<a name="line.8"></a>
<FONT color="green">009</FONT>     *     http://www.apache.org/licenses/LICENSE-2.0<a name="line.9"></a>
<FONT color="green">010</FONT>     *<a name="line.10"></a>
<FONT color="green">011</FONT>     * Unless required by applicable law or agreed to in writing, software<a name="line.11"></a>
<FONT color="green">012</FONT>     * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.12"></a>
<FONT color="green">013</FONT>     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.13"></a>
<FONT color="green">014</FONT>     * See the License for the specific language governing permissions and<a name="line.14"></a>
<FONT color="green">015</FONT>     * limitations under the License.<a name="line.15"></a>
<FONT color="green">016</FONT>     */<a name="line.16"></a>
<FONT color="green">017</FONT>    package org.apache.commons.jxpath.ri.compiler;<a name="line.17"></a>
<FONT color="green">018</FONT>    <a name="line.18"></a>
<FONT color="green">019</FONT>    import org.apache.commons.jxpath.NodeSet;<a name="line.19"></a>
<FONT color="green">020</FONT>    import org.apache.commons.jxpath.Pointer;<a name="line.20"></a>
<FONT color="green">021</FONT>    import org.apache.commons.jxpath.ri.EvalContext;<a name="line.21"></a>
<FONT color="green">022</FONT>    import org.apache.commons.jxpath.ri.model.NodePointer;<a name="line.22"></a>
<FONT color="green">023</FONT>    import org.apache.commons.jxpath.ri.QName;<a name="line.23"></a>
<FONT color="green">024</FONT>    import org.apache.commons.jxpath.util.ValueUtils;<a name="line.24"></a>
<FONT color="green">025</FONT>    <a name="line.25"></a>
<FONT color="green">026</FONT>    import java.util.Collections;<a name="line.26"></a>
<FONT color="green">027</FONT>    import java.util.Iterator;<a name="line.27"></a>
<FONT color="green">028</FONT>    import java.util.Locale;<a name="line.28"></a>
<FONT color="green">029</FONT>    <a name="line.29"></a>
<FONT color="green">030</FONT>    /**<a name="line.30"></a>
<FONT color="green">031</FONT>     * Common superclass for several types of nodes in the parse tree. Provides<a name="line.31"></a>
<FONT color="green">032</FONT>     * APIs for optimization of evaluation of expressions.  Specifically, an<a name="line.32"></a>
<FONT color="green">033</FONT>     * expression only needs to executed once during the evaluation of an xpath<a name="line.33"></a>
<FONT color="green">034</FONT>     * if that expression is context-independent.  Expression.isContextDependent()<a name="line.34"></a>
<FONT color="green">035</FONT>     * provides that hint.<a name="line.35"></a>
<FONT color="green">036</FONT>     *<a name="line.36"></a>
<FONT color="green">037</FONT>     * @author Dmitri Plotnikov<a name="line.37"></a>
<FONT color="green">038</FONT>     * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $<a name="line.38"></a>
<FONT color="green">039</FONT>     */<a name="line.39"></a>
<FONT color="green">040</FONT>    public abstract class Expression {<a name="line.40"></a>
<FONT color="green">041</FONT>    <a name="line.41"></a>
<FONT color="green">042</FONT>        /** zero */<a name="line.42"></a>
<FONT color="green">043</FONT>        protected static final Double ZERO = new Double(0);<a name="line.43"></a>
<FONT color="green">044</FONT>    <a name="line.44"></a>
<FONT color="green">045</FONT>        /** one */<a name="line.45"></a>
<FONT color="green">046</FONT>        protected static final Double ONE = new Double(1);<a name="line.46"></a>
<FONT color="green">047</FONT>    <a name="line.47"></a>
<FONT color="green">048</FONT>        /** NaN */<a name="line.48"></a>
<FONT color="green">049</FONT>        protected static final Double NOT_A_NUMBER = new Double(Double.NaN);<a name="line.49"></a>
<FONT color="green">050</FONT>    <a name="line.50"></a>
<FONT color="green">051</FONT>        private boolean contextDependencyKnown = false;<a name="line.51"></a>
<FONT color="green">052</FONT>        private boolean contextDependent;<a name="line.52"></a>
<FONT color="green">053</FONT>    <a name="line.53"></a>
<FONT color="green">054</FONT>        /**<a name="line.54"></a>
<FONT color="green">055</FONT>         * Returns true if this expression should be re-evaluated<a name="line.55"></a>
<FONT color="green">056</FONT>         * each time the current position in the context changes.<a name="line.56"></a>
<FONT color="green">057</FONT>         * @return boolean<a name="line.57"></a>
<FONT color="green">058</FONT>         */<a name="line.58"></a>
<FONT color="green">059</FONT>        public synchronized boolean isContextDependent() {<a name="line.59"></a>
<FONT color="green">060</FONT>            if (!contextDependencyKnown) {<a name="line.60"></a>
<FONT color="green">061</FONT>                contextDependent = computeContextDependent();<a name="line.61"></a>
<FONT color="green">062</FONT>                contextDependencyKnown = true;<a name="line.62"></a>
<FONT color="green">063</FONT>            }<a name="line.63"></a>
<FONT color="green">064</FONT>            return contextDependent;<a name="line.64"></a>
<FONT color="green">065</FONT>        }<a name="line.65"></a>
<FONT color="green">066</FONT>    <a name="line.66"></a>
<FONT color="green">067</FONT>        /**<a name="line.67"></a>
<FONT color="green">068</FONT>         * Implemented by subclasses and result is cached by isContextDependent()<a name="line.68"></a>
<FONT color="green">069</FONT>         * @return calculated context-dependentness as boolean<a name="line.69"></a>
<FONT color="green">070</FONT>         */<a name="line.70"></a>
<FONT color="green">071</FONT>        public abstract boolean computeContextDependent();<a name="line.71"></a>
<FONT color="green">072</FONT>    <a name="line.72"></a>
<FONT color="green">073</FONT>        /**<a name="line.73"></a>
<FONT color="green">074</FONT>         * Evaluates the expression. If the result is a node set, returns<a name="line.74"></a>
<FONT color="green">075</FONT>         * the first element of the node set.<a name="line.75"></a>
<FONT color="green">076</FONT>         * @param context evaluation context<a name="line.76"></a>
<FONT color="green">077</FONT>         * @return Object<a name="line.77"></a>
<FONT color="green">078</FONT>         */<a name="line.78"></a>
<FONT color="green">079</FONT>        public abstract Object computeValue(EvalContext context);<a name="line.79"></a>
<FONT color="green">080</FONT>    <a name="line.80"></a>
<FONT color="green">081</FONT>        /**<a name="line.81"></a>
<FONT color="green">082</FONT>         * Evaluates the expression. If the result is a node set, returns<a name="line.82"></a>
<FONT color="green">083</FONT>         * the first element of the node set.<a name="line.83"></a>
<FONT color="green">084</FONT>         * @param context evaluation context<a name="line.84"></a>
<FONT color="green">085</FONT>         * @return Object<a name="line.85"></a>
<FONT color="green">086</FONT>         */<a name="line.86"></a>
<FONT color="green">087</FONT>        public abstract Object compute(EvalContext context);<a name="line.87"></a>
<FONT color="green">088</FONT>    <a name="line.88"></a>
<FONT color="green">089</FONT>        /**<a name="line.89"></a>
<FONT color="green">090</FONT>         * Iterate over the values from the specified context.<a name="line.90"></a>
<FONT color="green">091</FONT>         * @param context evaluation context<a name="line.91"></a>
<FONT color="green">092</FONT>         * @return value Iterator<a name="line.92"></a>
<FONT color="green">093</FONT>         */<a name="line.93"></a>
<FONT color="green">094</FONT>        public Iterator iterate(EvalContext context) {<a name="line.94"></a>
<FONT color="green">095</FONT>            Object result = compute(context);<a name="line.95"></a>
<FONT color="green">096</FONT>            if (result instanceof EvalContext) {<a name="line.96"></a>
<FONT color="green">097</FONT>                return new ValueIterator((EvalContext) result);<a name="line.97"></a>
<FONT color="green">098</FONT>            }<a name="line.98"></a>
<FONT color="green">099</FONT>            if (result instanceof NodeSet) {<a name="line.99"></a>
<FONT color="green">100</FONT>                return new ValueIterator(((NodeSet) result).getPointers().iterator());<a name="line.100"></a>
<FONT color="green">101</FONT>            }<a name="line.101"></a>
<FONT color="green">102</FONT>            return ValueUtils.iterate(result);<a name="line.102"></a>
<FONT color="green">103</FONT>        }<a name="line.103"></a>
<FONT color="green">104</FONT>    <a name="line.104"></a>
<FONT color="green">105</FONT>        /**<a name="line.105"></a>
<FONT color="green">106</FONT>         * Iterate over the pointers from the specified context.<a name="line.106"></a>
<FONT color="green">107</FONT>         * @param context evaluation context<a name="line.107"></a>
<FONT color="green">108</FONT>         * @return pointer Iterator<a name="line.108"></a>
<FONT color="green">109</FONT>         */<a name="line.109"></a>
<FONT color="green">110</FONT>        public Iterator iteratePointers(EvalContext context) {<a name="line.110"></a>
<FONT color="green">111</FONT>            Object result = compute(context);<a name="line.111"></a>
<FONT color="green">112</FONT>            if (result == null) {<a name="line.112"></a>
<FONT color="green">113</FONT>                return Collections.EMPTY_LIST.iterator();<a name="line.113"></a>
<FONT color="green">114</FONT>            }<a name="line.114"></a>
<FONT color="green">115</FONT>            if (result instanceof EvalContext) {<a name="line.115"></a>
<FONT color="green">116</FONT>                return (EvalContext) result;<a name="line.116"></a>
<FONT color="green">117</FONT>            }<a name="line.117"></a>
<FONT color="green">118</FONT>            if (result instanceof NodeSet) {<a name="line.118"></a>
<FONT color="green">119</FONT>                return new PointerIterator(((NodeSet) result).getPointers().iterator(),<a name="line.119"></a>
<FONT color="green">120</FONT>                        new QName(null, "value"),<a name="line.120"></a>
<FONT color="green">121</FONT>                        context.getRootContext().getCurrentNodePointer().getLocale());<a name="line.121"></a>
<FONT color="green">122</FONT>            }<a name="line.122"></a>
<FONT color="green">123</FONT>            return new PointerIterator(ValueUtils.iterate(result),<a name="line.123"></a>
<FONT color="green">124</FONT>                    new QName(null, "value"),<a name="line.124"></a>
<FONT color="green">125</FONT>                    context.getRootContext().getCurrentNodePointer().getLocale());<a name="line.125"></a>
<FONT color="green">126</FONT>        }<a name="line.126"></a>
<FONT color="green">127</FONT>    <a name="line.127"></a>
<FONT color="green">128</FONT>        /**<a name="line.128"></a>
<FONT color="green">129</FONT>         * Pointer iterator<a name="line.129"></a>
<FONT color="green">130</FONT>         */<a name="line.130"></a>
<FONT color="green">131</FONT>        public static class PointerIterator implements Iterator {<a name="line.131"></a>
<FONT color="green">132</FONT>            private Iterator iterator;<a name="line.132"></a>
<FONT color="green">133</FONT>            private QName qname;<a name="line.133"></a>
<FONT color="green">134</FONT>            private Locale locale;<a name="line.134"></a>
<FONT color="green">135</FONT>    <a name="line.135"></a>
<FONT color="green">136</FONT>            //to what method does the following comment refer?<a name="line.136"></a>
<FONT color="green">137</FONT>            /**<a name="line.137"></a>
<FONT color="green">138</FONT>             * Create a new PointerIterator<a name="line.138"></a>
<FONT color="green">139</FONT>             * @param it underlying Iterator<a name="line.139"></a>
<FONT color="green">140</FONT>             * @param qname name<a name="line.140"></a>
<FONT color="green">141</FONT>             * @param locale Locale<a name="line.141"></a>
<FONT color="green">142</FONT>             * @deprecated Use the method that takes a NamespaceManager<a name="line.142"></a>
<FONT color="green">143</FONT>             */<a name="line.143"></a>
<FONT color="green">144</FONT>            public PointerIterator(Iterator it, QName qname, Locale locale) {<a name="line.144"></a>
<FONT color="green">145</FONT>                this.iterator = it;<a name="line.145"></a>
<FONT color="green">146</FONT>                this.qname = qname;<a name="line.146"></a>
<FONT color="green">147</FONT>                this.locale = locale;<a name="line.147"></a>
<FONT color="green">148</FONT>            }<a name="line.148"></a>
<FONT color="green">149</FONT>    <a name="line.149"></a>
<FONT color="green">150</FONT>            public boolean hasNext() {<a name="line.150"></a>
<FONT color="green">151</FONT>                return iterator.hasNext();<a name="line.151"></a>
<FONT color="green">152</FONT>            }<a name="line.152"></a>
<FONT color="green">153</FONT>    <a name="line.153"></a>
<FONT color="green">154</FONT>            public Object next() {<a name="line.154"></a>
<FONT color="green">155</FONT>                Object o = iterator.next();<a name="line.155"></a>
<FONT color="green">156</FONT>                return o instanceof Pointer ? o : NodePointer.newNodePointer(qname, o, locale);<a name="line.156"></a>
<FONT color="green">157</FONT>            }<a name="line.157"></a>
<FONT color="green">158</FONT>    <a name="line.158"></a>
<FONT color="green">159</FONT>            /**<a name="line.159"></a>
<FONT color="green">160</FONT>             * Unsupported.<a name="line.160"></a>
<FONT color="green">161</FONT>             */<a name="line.161"></a>
<FONT color="green">162</FONT>            public void remove() {<a name="line.162"></a>
<FONT color="green">163</FONT>                throw new UnsupportedOperationException();<a name="line.163"></a>
<FONT color="green">164</FONT>            }<a name="line.164"></a>
<FONT color="green">165</FONT>        }<a name="line.165"></a>
<FONT color="green">166</FONT>    <a name="line.166"></a>
<FONT color="green">167</FONT>        /**<a name="line.167"></a>
<FONT color="green">168</FONT>         * Value Iterator<a name="line.168"></a>
<FONT color="green">169</FONT>         */<a name="line.169"></a>
<FONT color="green">170</FONT>        public static class ValueIterator implements Iterator {<a name="line.170"></a>
<FONT color="green">171</FONT>            private Iterator iterator;<a name="line.171"></a>
<FONT color="green">172</FONT>    <a name="line.172"></a>
<FONT color="green">173</FONT>            /**<a name="line.173"></a>
<FONT color="green">174</FONT>             * Create a new ValueIterator.<a name="line.174"></a>
<FONT color="green">175</FONT>             * @param it underlying Iterator, may contain pointers<a name="line.175"></a>
<FONT color="green">176</FONT>             */<a name="line.176"></a>
<FONT color="green">177</FONT>            public ValueIterator(Iterator it) {<a name="line.177"></a>
<FONT color="green">178</FONT>                this.iterator = it;<a name="line.178"></a>
<FONT color="green">179</FONT>            }<a name="line.179"></a>
<FONT color="green">180</FONT>    <a name="line.180"></a>
<FONT color="green">181</FONT>            public boolean hasNext() {<a name="line.181"></a>
<FONT color="green">182</FONT>                return iterator.hasNext();<a name="line.182"></a>
<FONT color="green">183</FONT>            }<a name="line.183"></a>
<FONT color="green">184</FONT>    <a name="line.184"></a>
<FONT color="green">185</FONT>            public Object next() {<a name="line.185"></a>
<FONT color="green">186</FONT>                Object o = iterator.next();<a name="line.186"></a>
<FONT color="green">187</FONT>                return o instanceof Pointer ? ((Pointer) o).getValue() : o;<a name="line.187"></a>
<FONT color="green">188</FONT>            }<a name="line.188"></a>
<FONT color="green">189</FONT>    <a name="line.189"></a>
<FONT color="green">190</FONT>            /**<a name="line.190"></a>
<FONT color="green">191</FONT>             * Unsupported.<a name="line.191"></a>
<FONT color="green">192</FONT>             */<a name="line.192"></a>
<FONT color="green">193</FONT>            public void remove() {<a name="line.193"></a>
<FONT color="green">194</FONT>                throw new UnsupportedOperationException();<a name="line.194"></a>
<FONT color="green">195</FONT>            }<a name="line.195"></a>
<FONT color="green">196</FONT>        }<a name="line.196"></a>
<FONT color="green">197</FONT>    }<a name="line.197"></a>




























































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